And moses e



G. R BLODGETT, R. T. -HURLEY, AND M. E. CHENEY.

S PARK PLUG. APPLICATION FILED 1AN.5, I922.

Reissued Mar. 14, 1922.

INVENTOR e RBiodgeI? as 5. Chen 7 Tfiqr? G. R. BLUDGETT, R. T. HURLEY, AND M. E. CHENEY.

SPARK PLUG.

APPLICATION FILED JAN. 5. 1922.

Reissued Mar. 14, 1922.

- INVENTOR George 22.570496 Moses 5 C'/1e/1 UNITED STATES PATENT ol-rics- GEORGE B. BLODGETT, OF BROOKLYN, ROY T. HURLEY, OF NEW YORK, CEENEY, OF BROOKLYN, NEW YORK.

MOSES E.

SPARK PLUG.

Specification of Reissued Letters Patent. Reissued Mar, 14,, 1922,

Original No. 1,399,375, dated December 6, 1921, Serial No. 509,483, flle'd October 22, 1921. Application. for

' reissue filed January 5, 1922. Serial No. 527,171.

To all whom it may concern:

ROY T. HURLEY, and Mosns E. CHENEY, citizens of the United States, the said BLoDoE'r'r and CHENEY residents of Brooklyn, county of Kings, and State of New York, and the said HURLEY a resident of Bronx, county of Bronx, and State of New York, have in-v vented new and useful Improvements in Spark Plugs, of which the following is a specification.

Our invention relates to improvements in spark lugs. It has for its object to bring about t e production of spark plugs for use with cylinders of internal combustion engines of low compression ratios which shall be better adapted for the particular uses to which they are to be put and to produce spark plugs of the above character more efficient and durable and less liable to carbonization and pre-ignition in use than has heretofore been possible. It consists of the novel devices herein set forth.

Heretofore many attempts have been made to overcome the troubles of carbonization and pre-ignition so frequent in the use of spark plugs of the above general character. But so far none of these attempts have been entirely satisfactory or successful in overcoming the troubles. While many expedients have been suggested, more or less successful under certain specified conditions, none of them have resu ted in the production of spark plugs uniformly and durably free from these troubles.

We have discovered that there is a close relation-ship existing between the volume of the space within the spark plug surroundin the electrode and adjacent parts, into which space the gas flows from the cylinder and in which it is'burnt, the area of the walls of such space effective to receive, maintain and dispense heat, 'the manner and extent of admission of gas into the space, and the compression ratio of the engine cylinder with which the spark plug is to be used, and that, if the proper arrangement and proportions are secured in the manufacture of the spark plugs in these factors or particulars, the

resulting spark plugs produced will be well.

are intended to be put, will be more durable and will function better than ordinary spark plugs and that over a much wider range of compression ratios and under much greater changes in load conditions, will be freer from liability to carbonize or to pro-ignite and will generally give much more eflicient and satisfactory results; the gas introduced into the space within the spark plug will be brought into the very best condition for combustion, and the parts of the spark plug with which the gas comes into contact will be under ordinary runnin conditions brought into and maintained within the proper 11mlts of temperature to produce the best results,

adapted for the particular uses to which they Be it known that we, GEORGE R. BLoDcnTT,

neither low enough to permit carbonization plete combustion; thus securing the highest eificiency without leaving harmful roducts of combustion on the electrode, insu ation or other parts.

We have found that in engine cylinders there are two general classes of compression ratio, one that for convenience, we term high compresslon, including engine cylinders such as are used for aviation purposes, where compression is relatively high and speed constant, and low compression ratio, as in engine cylinders adapted for automobiles and marine purposes, where the com-' pression is lower and the speed variable. In this specification and claims we use the terms high and low compression ratio in this general sense. The present ap lication is addressed specifically to spark p ugs for use in low compression ratio engines.

In the accompanying drawings forming part hereof, we have illustrated our improvement in its preferred forms for varying conditions. Referring to the drawings Figures 1 and 2 represent spark plugs adapted for use with engine cylinders having a low compression ratio, Fig. 1 illustrating one adapted to be used with engine cylinders for automobiles, and Fig. 2 for marine purposes. In each of these figures, the view is a cenpart of the insulation ward toward the end 0 the central electrod 2. 7 is a space formed within the lower consisting of the interior surfaces of shell 1 and the exterior surfaces of the lower part of electrode 2, and of protruding portion 6 of the insulation. This space is of course filled with gas at each operation of theengine cylinder, which gas is exploded at the proper time during such operation. We have discovered that this space and the area of the surfaces of its surroundin walls effective to receive, maintain *an dispense heat, and the cross-sectional area of the 01'1- fice 8,-should be proportioned and arranged with reference to the compression ratio adapted to be developed under ordinary running conditions in the engine cylinder with which the spark plug is adapted to be used,

and when the proper relationship of the volume of such space, and the effective heat area of the surrounding walls and the crosssectional area of the orifice to one another and to the said compression ratio is obtained, the electrode and its ad acent parts, and the walls of the-shell will under ordiproper range of temperature, properly to condition the gas for the most complete com-.

bustion possibl at the proper moment, i. e. to bring it to and maintain it within the proper limits of temperature, on the one hand above the carbonization oint, i. e., not low enough to permit carbomzation, and on the other hand below. the pro-ignition point, i. e., not high enough to cause preignition. space and the effective heat area of its surrounding walls should be decreased as, the compression ratio increases and increased as that ratio decreases, although the rate of such decrease or increase is not exactly proportioned to the rate of increase or decrease in the compression ratio.

' Generally speaking, the orifice should be more orless restricted, depending upon the compression ratio. In general, as the compression ratio becomes higher, the orificeshould become larger in cross-sectional area, although this does not exactly vary in direct proportion to the rise in compression ratio. In other words, speaking generally, if the compression ratio is high, the area of the oriport of shell 1, the walls of the space In general, the volume of such fice should be largerand, if the compression is lower, the cross-sectional area of the orifice should be less.

The area of the walls of the space, re-

ferred to herein as effective area or ef-' side walls of the shell of metal, the exterior walls of the spindle and electrode usually of a different metal, the exterior walls of insulatin material, which ma vary in different pugs, etc. These su tances have different heat capacity, conductivity, .etc., and during normal running conditions one part will run hotter than another part, for. example, and thus im art more heat to the unexploded gas in t e s ace. There are thus two factors entering into the effective heating work done by these different parts of the walls of the space, one the actual physical area of a part and the other the relative capacity of the part to absorb, hold and give out heat to such gas. Manifestly the total of effective heating work or capacity therefor in the walls is the sum of the roducts of the areas of actual physical sura ces by the said relative heating capacity of each surface, such capacity being the ratio of; the actual .temperature of the said surface under normal running conditions to the temperature requiredto condition fuel, i. e., the temperature just below that of the pre-ignition oint. This for conciseness we term the elfhctive area or effective heat area and ach of the terms is used with this meaning throughout the specification and claims. The actual temperature of any of the parts under normal running conditions such as t e surface of the central electrode,

we will assume that the actual physical surface of the electrode in any particular case is one square centimeter. The actual temperature underv normal running conditions of the surface of the electrode is determined to be 1900 F. absolute and the temperature required to condition the fuel in this particular case is 1135 F. absolute,vthen the effective heating surface of the electrodewould be the product of itsarea 1 by the ratio of Hag whichis 1.67 square centimeter. The effective area of each of the other parts is computed in the same way.

Figs. 1 and 2 illustrate spark plugs adapted to beused with en 'ne cylinders of a relatively low degree o compression ratio.

The spark plug of Fig.1 is adapted to be in length an used with engine cylinders of automobiles, and that of Fig. 2 with engine cylinders of marine engines, in which the compression ratio is usually still lower than that of en- 5 inc cylinders adapted for automobile use. he corresponding parts of the spark, plug of F ig. 2 are numbered to correspond with similar parts of the spark plu of Fig. 1. In Fig.2 it will be notedthat t e space 7 is larger or has a larger volume than that in Fig. 1, and the surface area of the parts constituting the walls of the space in Fi 2 is larger than that of the correspomfing parts in F ig. 1. Theorifice 8 0f the spark plug of Fig. 2 has a cross-sectional area of less size than that ofFig. 1. In Figs. 1 and 2, the restricted opening 8 in each case is shown as made by means of a cap 10 having a restricted circular central opening.

Fig. 3 is a central section through an engine cylinder having a low compression ratio and represents an engine cylinder such as the spark plug of Fig. 1 is adapted to be used with. At its upper end it. is shown connected to a spark plug similar to Fig. 1. Fig. 3 is drawn diagrammatically to represent the range of displacement and corre sponding compression ratios in low ratio compression cylinders. For this purpose the right half of the figure represents substantially about the highest limit of displacement or ratio of compression, and the left hand part of the figure represents about the lowest limit of displacement and the lowest limit of compression ratio in low compression cylinders. In each half 11 re resents the lower end in each case of the cy linder and the distance between that in each instance and the dotted line 12 represents the length of stroke of the piston, and the distance from the dotted lines to the upper end of the cylinder represents in each instance the compression chamber of the cylinder. In one case the stroke is 4 inches, and in the other 5 inches. In the left hand half the com ression chamber is 1.6 inches in the right hand half it is 1.25 inches in length. 13 represents the outer walls of the cylinder, 14 the inner walls, and 15 an intervening s ace for a cooling fluid. The other parts 0 the cylin-v der and its connections are not shown in detail, being of any ordinary construction and forming no part of our invention.

55 While the limits of compression ratio and corresponding limits of volume of the space surrounding the electrode and adjacent parts and of the effective area of the surface of the walls of said space cannot be compression cylinders, we have found that under ordinary runnin conditions they are about as follows: For ow compression engines adapted for automobile and marine 05 use, namely, those in which the compression stated exactly for thediflferent classes of low ratio under ordinary running" conditions will range lower than about 5 to 1, the limits will generally ran e from about 5 m 1 to about 3 to 1, the v0 ume of the space should range from about 1.25 cubic centimeters to about 1.75 cubic centimeters, and the effective area of the surface of the walls of the space should range from about 13. square centimeter: to about 36. square centimeters.

Restriction of the orifice and especially in proper relationship to the other factors referred to above, assists in securing the proper amount of-(gas'in the spark plug on .each operation an in bringing that gas to the proper temperature and condition for explosion. Where an opening to a spark plug is unrestricted there are apt to be devious currents interfering with bringing the gas into proper condition for explosion, while with a restricted opening there is a positive swirling flow inward before explosion and outward after explosion, and the fuel fluid is more thorou hly brought into contact with the walls of t e space inside bf the plug, tending to bring it into proper condition.

The restriction of the orifice tends also to separate the space inside of the spark plug from the space inside of the cylinder more than would otherwise be the case, thus preventing too great and sudden rushes from the cyllnder of cold gas before explosion and of intensely heated gas after explosion, and also permitting the gas within the space in the spark plug to be brought into better no condition for combustion than is possible with the gas in the cylinder generally.

In low compression engines for automobile and marine use where the compression ratio varies as above stated, the cross-sectional area of the orifice should vary from about .20 square centimeters to about .10 square centimeters.

One application of our improvement is to take any specific core and shell construction of spark plug, meaning by that a special arrangement, form, shape, size, etc., of central spindle, surrounding insulation, central electrode and surrounding shell, etc, and vary or adapt the orifice to cause such spark plu to become fitted for use with an desire low compression ratio of en 'ne cy inder, or to adapt it so that it will within said limits cover a wide range of 'com pression ratios. While this can be carried out under the general principles laid down above, we have discovered that the best cross-sectional area of orifice in such in-. stances cited can be, derived from the following formula, namely, O:Kr, in which 0 represents the cross-sectional area,,of the orifice, 7' the compression ratio of cylinder," and in which K and n are constants of the particular core and shell construction. The

value of the constants K and n for any pardeterminedby taking two spark plugs of,

ticular core and shell construction can be the same core and shell construction except that the orifices in the two cases will vary. The two plugs are then tested upon cylinders of difi'erent compression ratios until in each case the compression ratio is determined with which the spark plug gives best results. Such tests are well known to those skilled in the art and need not be described in detail except to say thatin making such tests the highest c'ompressionratio in each case is determined with which the spark plug will function without pre-ignition and that compression ratio is taken as that at which, under normal running conditions, thespark plug gives the best results. The phrase gives best results? is used throughout the specification ,and claims with this meaning.

The values of all the factors now being known, the net value of O can be determined in the original formula, OzKr; 7

By addlng to the said net value of O the cross-section of the centralelectrode and the projected surface of the side electrode, the gross area and diameter of orifice can be obtained.

Our improved spark plugs are durable, eiiicient, not liable to carbonization or preignition in use even over a wide range of compression ratios and load conditions.

What we claim as new and desireto se-- cure by Letters Patent is:

1. In a spark plug adapted for use in connection with cylinders of internal combustion engines havlng a compresslon rat1o lower than 5 to 1, the combination of an electrode and a shell provided with a space,

to be filled with gas from the cylinder, surrounding the electrode and adjacent parts, and a restricted orifice adapted to connect the space withthe cylinder ofan engine, the relative, proportions of the volume of the space within the spark plug and the efiective area of surface of the walls of said space and the cross-sectional area of the orifice to one another being substantially as follows: the volume of said space being within about 1.75-cubic centimetersto about 1.25 cubic centimeters, the elfectiv'e area of surface of the walls of said space being within about 36. square centimeters to about 13. square centimeters, and the cross-sectional area of the-orifice being within about 0.10 square centimeters to about .20 square centimeters.

2. The combination of. a cylinder of an internal combustion engine having a low compression ratio, a spark plug fitted into a wall of the cylinder, having an electrode and a shellprovided with a space, to be filled with gas from the cylinder, surrounding the electrode and adjacent parts, and a restricted orifice adapted to connect the "and are determinable from two spark plu volume of said space being within about 1.7 5

cubic centimeters to about 1.25 cubic centimeters, the effective area of the surface of the Walls of said space being within about 36.v square centimeters to about 13. square.

centimeters, and the cross-sectional area of the orifice being within about 0.10 square centimeters to about 0.20 square centimeters, 3. In a sparkplug adapted for use with a. specific low compression ratio or range of low compression ratios of cylinder of internal combustion engines, the combination of a specific core and shell construction forming a space around the electrode and adjacent parts of a specific volume and having a'specific e'fi'ective area of surface for the walls of said space, and a restricted orifice for said space of a cross-sectional area of the value o-f.() in the formula O=Kr, where K and a are constants dependin upon the said construction of core and shel of'the said construction of core and shel but difi'ering fromeach other in cross-sectional area of orifice, when each sparkplu is used with the compression ratio adapte to give the best results for said spark plug. 4. The combination of a cylinder of. an internal combustion engine of a specific low compression ratio,-a spark plug fitted into the walls of said cylinder, and having a specific construction of core and shell containing a space around the electrode and adjacent parts of a specific volume, and having a s ecific effective area of surface for the wal of said space, and a restricted orifice to the spark plug of a cross-sectional area of the value of O in the formula O=Kr, where K and n are constants, de-

a an electrode and a shell provided with a space, to be filled with gas from the cylinder, surrounding the electrode and adjacent parts, and a restricted orifice ada ted to connect the space with the cylinder, t e relaanother being substantially as follows: the the orifice being Within about 0.10 square volume of said space being Within about 1.75 centimeters to about 0.20 square centimeters.

cubic centimeters to about 1.25 cubic centi- In testimony whereof We have signed our 10 meters, the effective area of the surface of names to this specification.

the walls of said space being within about GEORGE R. BLODGETT.

36. square centimeters to about 15. square ROY T. HURLEY.

centimeters, and the cross-sectional area of MOSES E. CHENEY. 

